中文摘要：

目的：探讨X线交叉互补基因1（XRCC1）外显子C26304T、G27466A和G28152A三处最常见的单核苷酸多态性（single nucleotide polymorphism，SNP）与乳腺癌的关系。方法：以自然人群为基础的病例对照研究方法，对84例乳腺癌患者组和以1：3成组频数匹配原则获得的252例对照组进行研究，XRCC1 C26304T、G27466A和G28152A SNPs基因分型采用聚合酶链反应-限制性内切酶片段长度多态性（polymerase chain reaction—restriction fragment length polymorphism，PCR—RFLP）分析方法。单体型分布采用EH linkage software 1．2分析软件进行预测和比较。结果：乳腺癌患者组和对照组吸烟状况分布差异有显著性，病例组曾经或现在吸烟个体比例7．1％明显高于对照组2．0％（P〈0．05），性别、年龄、饮酒状况及一二级亲属家族恶性肿瘤史等基本特征因素分布差异均无显著性（P〉0．05）。C26304T、G27466A和G28152A SNPs多态基因型和多态等位基因分布在两组间分布差异均无显著性（P〉0．05）。经上述因素校正后，XRCC1 SNPs与乳腺癌发病没有显著相关关系（P〉0．05）。应用EH linkage software 1．2单体型分析软件显示，XRCC1 SNPs在各组内均存在连锁不平衡现象，CGG、CGA、CAG和TGG是最常见的4类单体型。单体型组间分布同样不存在显著性差异（P〉0．05）。结论：XRCC1 C26304T、G27466A和G28152A SNPs与乳腺癌的风险没有相关关系，各SNPs存在连锁不平衡现象，CGG、CGA、CAG和TGG是最常见的4类单体型。

英文摘要：

Objective. To examine the contribution of the three most common single nucleotide polymorphisms （SNPs） in XRCC1 gene, C26304T, G27466A and G28152A, to susceptibility of breast cancer in Chinese Han population. Methods： In this population-based case control study, 84 cases with breast cancer and 252 controls ,matched to the cases in terms of habitation and age （5 years）,were genotyped for the XRCC1 C26304T,G27466A and G28152A polymorphisrns by polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） methods. The haplotype distribution was estimated and compared by EH linkage software 1.2. Results. The distribution of basic characteristics ,such as age ,alcohol drinking ,the family history of malignancy in first and second relatives except cigarette smoking, were not significantly different between cases and controls. However, the percentage of ever or current smokers was significantly higher in cases （7. 1%） than that in controls （2. 0%）. The distributions of allelotype and genotype of C26304T,G27466A and G28152A polymorphisms were also not significantly different between cases and controls. There was no significant association between the risk of breast cancer and these three SNPs of XRCC1 gene. The genetic linkage disequilibrium existed in these three polymorphic sites both in cases and controls,in which the CGG,CGA,CAG and TGG haplotypes were the most common. There was also no significant association of XRCC1 haplotype with risk of breast cancer. Conclusions： XRCC1 C26304T, G27466A and G28152A SNPs may not be associated with the susceptibility of breast cancer. The CGG,CGA,CAG and TGG haplotypes might be the most common haplotypes in Chinese Han population.